Federal investigators have scoured Omar Mateen's laptop computer, cell phone and the trail of communications he left behind and so far have found no evidence that he led a secret gay life, according to officials who spoke on the condition of anonymity about the ongoing investigation.

They've also reviewed the electronic devices of men who said they'd communicated with him on gay dating apps and so far have found no link.

Mateen is the 29-year-old Fort Pierce security guard who opened fire at Pulse, a gay Orlando nightclub, on June 12, killing 49 people and injuring more than 50 others.

He was killed in a gun battle with Orlando police when they stormed the building shortly after 5 a.m., ending an assault and standoff that lasted three hours.

Investigators have not stopped following leads about Mateen's reported interest in gay clubs and gay men, but federal officials reported Thursday that they've found no photographs, text messages, smart phone apps or gay pornography that suggest Mateen was gay or was trying to find a gay lover.

Pictures from the aftermath of a mass shooting at Pulse nightclub in Orlando that left 49 victims dead and another 53 injured. Click here for more coverage on the massacre.

The investigation, however, is far from over.

Four men have told the Orlando Sentinel that they saw Mateen in the club before June 12.

Two of those men and one other said they'd communicated with Mateen via gay dating apps.

Other men have given similar accounts to other news organizations.

Cord Cedeno was one of the men who told the Sentinel that he'd seen Mateen at Pulse previously and had interacted with him on gay dating apps.

Cedeno on Thursday said he stood by his account.

Kevin West of Orlando, told the Sentinel he'd chatted often with Mateen on the gay app Jack'd, and said he believes Mateen was smart enough to not leave a record of his activity by deleting accounts or using multiple phones.

"It's almost certain that he covered his tracks," West said. "Lots of people are still secretive about it. They say they don't show their face online because, 'I'm not out to my family, or because of my career.' "

Federal investigators, however, believe men making such claims may be confusing Mateen with someone else or are not credible, the officials said.

On Wednesday, Univision, a Spanish-language broadcaster, aired the account of a man who said he'd had sex with Mateen 15 to 20 times in an affair that ended in December.

FBI spokeswoman Amy Pittman would not say whether investigators have spoken to that man or recovered security camera video from an Orlando hotel where he and Mateen were reported to have rendezvoused.

"We are not at liberty to confirm or deny specific interviews, nor the credibility of content … due to the ongoing investigation," she wrote in an email.

Federal officials in Washington, however, said they do not believe that man's claims are credible.

At a Tuesday news conference in Orlando, U.S. Attorney General Loretta Lynch was asked if the FBI had linked Mateen to other gay clubs.

Her answer: "We are following every lead."

Mateen's ex-wife, Sitora Yusifiy, told CNN last week that she witnessed Mateen's father call him gay.

Asked if she thought Mateen was gay, she said, "I questioned it in my own head when I was with him. He would do a lot of things, little things that would definitely make any woman question whether he was or not."

The FBI has not yet determined why Mateen chose to attack Pulse, a club about 120 miles north of where he lived, officials said.